<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>变量定义</title>
</head>
<body>
<script type="text/javascript">
  var job;
  var name = "张三丰";
  age = 100;
  alert("job=" + job);
  alert("name=" + name);
  alert("age=" + age);
</script>
</body>
</html>